Do Worms Eat Seaweed? (What about Kelp and Seagrass?)

Worms eat most natural decaying matter, like fruit and vegetables food scraps, other organic kitchen scraps, the nutrients from dead leaves, petals and roots, and yes, even decomposing seaweed!

Freshwater seaweed is pretty much fine to go directly onto your garden or in your composting bin, however, it is important to pay attention to the effects that the seaweed is having on your bin.

Yes, worms do eat seaweed.  Seaweed is natural but comes from a different environment to the average garden worm, so what effects can it have on them?

Depending on the source of the seaweed, it can be good or bad for your farm. It’s essential to be sure of the source of the seaweed in order to deal with it correctly for your farm!

Can you put seaweed in a worm farm? 

Yes, you can put seaweed in a worm farm or compost bin. Some even believe trace amounts of seaweed are miracle composting materials.

But, just as with all things in nature, it is essential to find the right balance.

So, it might be wise to start by loading a little seaweed into your compost bin and waiting to see the results before adding more.

A great idea, as always with any material, is to do your research on the specific seaweed you have. Here are some tips:

  • It is crucial to know the source of the algae.
  • Freshwater algae tends to be perfectly fine as is for worm composting bins, however ocean algae can be dangerous.
  • Saltwater sea weed is, as the name suggests, covered in salt.

Due to that being on the algae, it could be very damaging to your farm and to your plants and to your entire garden!

Worm poop, also known as worm castings, is good at retaining water in order to keep your plants and flowers hydrated for longer.

On the other hand, salt will absorb the water quicker and could dry out your vegetation, causing it to die.

For the worm bin itself, the salt on the algae can be dangerous to the worms! They need a damp environment in order to survive, as they breathe through their skin.

If you do plan on using saltwater algae, then remember to give it a rinse before putting it in your worm farm or on your garden! 

Can worms eat kelp? 

Yes, worms can eat kelp. But what exactly is kelp?

Kelp is a large variety of seaweed that is found in the oceans and that you may find quite regularly on your local beaches.

Kelp, being a saltwater algae, is covered with, and partially infused with salt. In order for it to be perfectly fine to eat, it is important to rinse the kelp before feeling it to your little friends, the worms.

Yet another thing to take into consideration when vermicomposting is the wetness of the kelp.

Although using unwashed kelp can be dangerous to your worms due to the salt level, it can be just as dangerous to insert too much wet kelp in your composting bin!

Do worms eat seagrass? 

Yes, worms do eat seagrass. However, it’s not an essential organic part of their meal.

Just as with anything from the sea that you may be considering giving to your worms, it is important to know where the seagrass is from and to give it a good rinse before giving it to your worms! 

When we shop for our food, we like to check the source of the products, in case they may come from a place where pollution or other toxins could have made its’ way into the food.

The same should be done for the nutrients you plan on giving the worms in your compost farm.


In short, it’s perfectly fine to add sea weed, kelp and more to your worm compost. However, to encourage plant growth and to keep your plants healthy, you must always rinse it beforehand.

Try a few small pieces and see how you get on. If you would like to learn more about what worms eat, check out our recent posts on soil and grass.